As it probably will happen, <a href="http://www.newscientisttech.com/article.ns?id=dn12278">there will be GPS receivers that use both systems</a>.

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The US-run Global Positioning System (GPS) is the most widely used satellite-navigation system in the world. But the EU wants to have alternative that is not under US control, and is developing its own system called Galileo, which has yet to be launched. The benefits of a US-EU agreement will depend on makers of receivers making use of both systems, but one senior US official involved in the talks says this is inevitable. "The market probably will drive dual-use receivers," said Raymond Clore, a GPS-Galileo senior adviser from the US State Department. "It just doesn't make sense to limit yourself to just one system."